Calibration

1. An active transceiver array for a wireless telecommunications network comprising: a central processing unit and a plurality of calibratable transceiver modules; the central processing unit comprising a primary signal generation unit; each transceiver module comprising: a transceiver chain operable to process a primary signal and generate a processed primary signal; a comparator unit operable to compare said primary signal and said processed primary signal to determine a transceiver chain error induced by said transceiver chain in said processed primary signal; and a correction unit which uses the transceiver error to correct said primary signal to be processed by said transceiver chain; wherein each transceiver chain comprises a digital connection to the central processing unit, a digital to analog converter and an antenna element; and wherein each module further comprises a coupling, operable to couple the transceiver chain to the comparator unit, the coupling being provided between the digital to analog converter and the antenna element.

2. An active transceiver array according to claim 1 , wherein the primary signal generation unit is operable to generate a different primary signal for each of said plurality of transceiver modules.

3. An active transceiver array according to claim 1 , further comprising a phase stable distribution element operable to distribute said primary signal to each of said plurality of transceiver modules.

4. An active transceiver array according to claim 3 , wherein said phase stable distribution element is operable to distribute said primary signal to said comparator unit of each of said plurality of transceiver modules.

5. An active transceiver array according to claim 3 , wherein said phase stable distribution element is operable to distribute the same said primary signal to said comparator unit of each of said plurality of transceiver modules.

6. An active transceiver array according to claim 3 , wherein said phase stable distribution network comprises a standing wave line.

7. An active transceiver array according to claim 1 , wherein said correction unit comprises a digital signal modification unit.

8. An active transceiver array according to claim 1 , wherein said correction unit comprises an RF phase and amplitude adjuster.

9. A calibratable transceiver module for use in an active transceiver array in a wireless telecommunications network, comprising: a transceiver chain operable to process a primary signal and generate a processed primary signal; a comparator unit operable to compare said primary signal and said processed primary signal to determine a transceiver chain error induced by said transceiver chain in said processed primary signal; and a correction unit which uses the transceiver error to correct said primary signal to be processed by said transceiver chain; wherein the transceiver chain comprises a digital to analog converter, an antenna element, and a digital connection to a central processing unit; and wherein the module further comprises a coupling, operable to couple the transceiver chain to the comparator unit, the coupling being provided between the digital to analog converter and the antenna element.

10. A method of calibrating an active transceiver array in a wireless telecommunications network comprising a plurality of transceiver modules and a central processing unit comprising a primary signal generation unit; said method comprising the steps, for each module, of: processing a primary signal in a transceiver chain to generate a processed primary signal; comparing said primary signal with said processed primary signal using a comparator unit to determine a transceiver chain error induced by said processing of said primary signal by said transceiver chain; and correcting said primary signal to be processed by said transceiver chain using said determined transceiver chain error; wherein each transceiver chain comprises a digital connection to the central processing unit, a digital to analog converter and an antenna element; and wherein each module further comprises a coupling, operable to couple the transceiver chain to the comparator unit, the coupling being provided between the digital to analog converter and the antenna element.

11. A method according to claim 10 , wherein said primary signal comprises a traffic signal.

12. A method according to claim 10 , wherein the steps are performed consecutively for each module forming part of the transceiver array.

13. A method according to claim 10 , wherein said primary signal comprises a sinusoidal test signal, and said method further comprises the steps of: sweeping said sinusoidal test signal in frequency and, based on said determined transceiver chain error, determining a phase length of said transceiver chain.